Special Digest Third editionConcrete in aggressive groundBRE Construction Division BRE is committed to pro. Download Citation on ResearchGate | BRE report – Concrete in aggressive grounds: An introduction to BRE Special Digest 1 | The codes and standards for. The introduction of the edition of BRE Special DIgest 1 (SP1) provides the guidance on concrete in sulfate-bearing ground. The range of exposure.
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In contrast, BS guidance for concrete has integrated the provisions for resistance to chemical attack into the numerous other requirements for practical concrete specification; for example, strength class and consistence, resistance speccial alkali—silica reaction and chloride content sigest respect of corrosion of reinforcing steel. These are the most commonly encountered locations. The Design Sulfate Class for the location should then be taken as the highest of the sulfate classes derived by the differing procedures.
Model procedures for the management of land contamination. Later the benefits of using fly ash or pulverized fuel ash pfa and blastfurnace slag-based cements were appreciated. In several cases of serious deterioration to concrete from TSA in the foundations of highway bridges , a major contributory factor was that the foundations had been constructed in excavations that were subsequently backfilled with pyritic clay and also comcrete to ingress of water.
These data should be used to plan the ground investigation.
SD 1 Concrete in aggressive ground. 3rd edition, BRE – Publication Index | NBS
As noted in Section C2. For soil, the sulfate analysis, expressed as SO4, should be on a 2: Also, the mobility of any groundwater must be known for some categories of concrete construction since site drainage may need to be designed to protect groujd foundations.
Sulfate Class This is a five-level classification of sulfate concentration that is applied to individual series of tests on soil or groundwater. The procedure for the latter is specifically included owing to severe TSA found in highway sub-structures embedded in pyrite-bearing Lower Lias Clay fill; generation of sulfate due to oxidation of the pyrite following ground disturbance proved to be a major factor.
It is calculated as the sum of sulfates already present in the ground, plus those that may result from oxidation of pyrite or similar minerals Section C5. This is sometimes called salt weathering Section B6.
Sulfate class limits based on 2: Composition, specifications and conformity criteria for low early strength blastfurnace cements BS EN It gives procedures for the determination of Design Digeat Class DS Condrete from soluble sulfate and magnesium, and from the potential sulfate eg from oxidation of pyrite. They also cover the more rarely occurring aggressive carbon dioxide found in some ground and surface waters.
As a result of new research findings Section A3 and the revision of guidance on the composition of concrete for given DC Classes Section D5. The change stems from findings of numerous ground investigation studies carried out by BRE and others following discoveries of the thaumasite form of sulfate attack TSA in the concrete foundations of highway structures.
In this case the recommended APM may often be achieved by redesigning the construction so that the concrete remains surrounded by impermeable ground that forms a barrier to movement of aggressive groundwater; for example, using a piled foundation or trenchfill foundation for a structure rather than a spread footing constructed in an open excavation. Assessing the aggressive chemical environment C4 Site investigation for aggressive ground conditions 23 For all locations an appraisal should be made of the groundwater conditions and, in particular, whether concrete could be exposed to mobile or flowing groundwater Section C3.
This immediately reacts with water to form hydrogen sulfide H2Sa gas that rises into the air space above the sewage.
Some important changes have been made to the previously published guidance. The procedure for taking account of the measured chloride content in this particular circumstance is given in Section C5.
Examples of such serious consequences could include: As in the previous cases, the concrete contained carbonatebearing aggregates[1,4—6]. It also gave recommendations for further research on the occurrence of TSA and mitigating measures. This cracking, together with white crystalline accumulations, are the characteristic grounv of the conventional form of sulfate attack.
A compressive strength requirement has never formed part of BRE recommendations for sulfate resistance.
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At times of low water table generally early summer to mid-autumnit will often be difficult to prove static groundwater conditions from digfst tests. BRE has underpinned this approach by issuing a series of guidance notes and Digests, dating back toon the causes of chemical attack and how to specify chemically resistant concrete.
These stem from a further study of occurrences of sulfate attack in concrete structures, and recent field and laboratory research Section A3. The contract may include also: Examples based on Table D1 are: